Re: task hung in port100_send_cmd_sync

On 18/09/2022 15:22, Rondreis wrote:
> Hello,
> 
> When fuzzing the Linux kernel driver v6.0-rc4, the following crash was
> triggered.

Hi,

Thanks for the report.

> 
> HEAD commit: 7e18e42e4b280c85b76967a9106a13ca61c16179
> git tree: upstream
> 
> kernel config: https://pastebin.com/raw/xtrgsXP3
> C reproducer: https://pastebin.com/raw/hjSnLzDh
> console output: https://pastebin.com/raw/3ixbVNcR
> 
> Basically, in the c reproducer, we use the gadget module to emulate
> attaching a USB device(vendor id: 0x54c, product id: 0x6c1, with the
> printer function) and executing some simple sequence of system calls.
> To reproduce this crash, we utilize a third-party library to emulate
> the attaching process: https://github.com/linux-usb-gadgets/libusbgx.
> Just clone this repository, install it, and compile the c
> reproducer with ``` gcc crash.c -lusbgx -lconfig -o crash ``` will do
> the trick.
> 
> I would appreciate it if you have any idea how to solve this bug.

You can try to bisect. Or you can build kernel with lockdep and try to
reproduce.

> 
> The crash report is as follows:

It's not a crash, but a blocked task, so there might be deadlock,
incorrect synchronization or some missing cleanup path. Actually quite a
lot could lead to this.

Best regards,
Krzysztof